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* [PATCH -next] nbd: add the check to prevent overflow in __nbd_ioctl()
@ 2021-07-31  1:48 Baokun Li
  2021-07-31 14:57 ` Jens Axboe
  0 siblings, 1 reply; 2+ messages in thread
From: Baokun Li @ 2021-07-31  1:48 UTC (permalink / raw)
  To: josef, axboe, linux-block, nbd, linux-kernel
  Cc: patchwork, libaokun1, Hulk Robot

If user specify a large enough value of NBD blocks option, it may trigger
signed integer overflow which may lead to nbd->config->bytesize becomes a
large or small value, zero in particular.

UBSAN: Undefined behaviour in drivers/block/nbd.c:325:31
signed integer overflow:
1024 * 4611686155866341414 cannot be represented in type 'long long int'
Call trace:
 handle_overflow+0x188/0x1dc lib/ubsan.c:192
 __ubsan_handle_mul_overflow+0x34/0x44 lib/ubsan.c:213
 nbd_size_set drivers/block/nbd.c:325 [inline]
 __nbd_ioctl drivers/block/nbd.c:1342 [inline]
 nbd_ioctl+0x998/0xa10 drivers/block/nbd.c:1395
 __blkdev_driver_ioctl block/ioctl.c:311 [inline]

Although it is not a big deal, still silence the UBSAN by limit
the input value.

Reported-by: Hulk Robot <>
Signed-off-by: Baokun Li <>
 drivers/block/nbd.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index c38317979f74..7c838bf8cc31 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1398,6 +1398,8 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 	case NBD_SET_SIZE:
 		return nbd_set_size(nbd, arg, config->blksize);
+		if (arg && (LLONG_MAX / arg <= config->blksize))
+			return -EINVAL;
 		return nbd_set_size(nbd, arg * config->blksize,

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2021-07-31  1:48 [PATCH -next] nbd: add the check to prevent overflow in __nbd_ioctl() Baokun Li
2021-07-31 14:57 ` Jens Axboe

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